Modern irrigation systems, such as lawn sprinklers, usually include multiple watering zones. The user typically sets an irrigation control timer to set the frequency and duration of watering for those zones. At the pre-programmed time, the system cycles through the various watering zones.
Simple irrigation systems often waste water because the programmed watering time occurs immediately before, during or after a natural rainstorm event. More expensive systems address this problem by employing a rain sensor. After a set amount of rain has fallen, the sensor engages a switch that will prevent the timer from watering (e.g., http://www.rainbird.com/landscape/products/controllers/RSD.htm). U.S. Pat. No. 7,949,433 describes the use of a rain threshold to enable or disable power to an irrigation system. An interface unit is connected in series with the common line of the sprinkler activation lines. When the interface unit determines or receives an indication that a rain threshold has been exceeded and/or that other criteria have been met, the interface unit inhibits the switching device, breaking the common line. This effectively disables all electrical signals via the activation lines to the valves, until the switch is closed. In this way, the irrigation control timer 30 is not aware that the watering has been interrupted or overridden.
One significant drawback of rain sensors is that, since they have no weather prediction or forecast capability, they ignore rainfall that occurs soon (i.e., within 24-hours) after the programmed watering time. If this happens, over-watering occurs and water is wasted. The cost of water in numerous urban areas has led to more sophisticated and purportedly effective irrigation solutions, some of which take weather predictions and forecasting into account.
Another drawback of rain sensors is that they are restricted to watering only on a fixed pattern of days (usually on specific days of the week) set by the sprinkler timer. This is inherently sub-optimal, since watering may be forced to occur shortly after a recent rain event, in order to ensure that enough watering occurs before the next allowable watering day.
U.S. Pat. No. 7,883,029 discloses an irrigation system including a radio transmitter station that transmits weather prediction information to a geographic region that includes multiple geographic sub-regions. The weather prediction information includes a respective geographic sub-region code for each of the geographic sub-regions for which a weather forecast predicts rain within a predetermined time period. An irrigation apparatus in a particular sub-region activates to water a watering zone at a schedule time. However, if the irrigation apparatus receives the sub-region code for the particular sub-region where the irrigation apparatus is located, the irrigation apparatus does not immediately activate to water the watering zone in one embodiment. The transmitter station may transmit both program content and data content on a common radio frequency signal wherein the data content includes the weather prediction information.
The use of weather information via the Internet for sprinkler control has been suggested before, as in the OpenSprinkler project: http://rayshobby.net/?page_id=160&http://rayshobby.net/blog/?p=1500. Other systems take advantage of radar data. U.S. Pat. No. 6,850,819, for example, resides in an irrigation control system that comprises a meter to measure one or more weather conditions, a monitor to examine rainfall data derived from radar scanning and to extract data which is representative of the scanned rainfall; and a controller to calculate a moisture content value, a predetermined moisture content value, and regulate irrigation in accordance with the computed values.